The grades on a physics midterm at Almond are normally distributed with $\mu = 72$ and $\sigma = 2.5$. Nadia earned a $66$ on the exam. Find the z-score for Nadia's exam grade. Round to two decimal places.
A z-score is defined as the number of standard deviations a specific point is away from the mean We can calculate the z-score for Nadia's exam grade by subtracting the mean $(\mu)$ from her grade and then dividing by the standard deviation $(\sigma)$ $ { z = \dfrac{x - {\mu}}{{\sigma}}} $ $ { z = \dfrac{66 - {72}}{{2.5}}} $ ${ z \approx -2.40}$ The z-score is $-2.40$. In other words, Nadia's score was $2.40$ standard deviations below the mean.